INVESTMENTS - Composition of Investments in Unrealized Loss Position (Detail)	Sep. 30, 2016	Dec. 31, 2015
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	100.00%	100.00%
Percentage of Total Unrealized Losses	100.00%	100.00%
Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	92.00%	97.00%
Percentage of Total Unrealized Losses	85.00%	95.00%
Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	4.00%	3.00%
Percentage of Total Unrealized Losses	11.00%	5.00%
Equity securities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	4.00%	0.00%
Percentage of Total Unrealized Losses	4.00%	0.00%
Japan government and agencies | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	4.00%	0.00%
Percentage of Total Unrealized Losses	2.00%	0.00%
Municipalities | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	1.00%	0.00%
Percentage of Total Unrealized Losses	1.00%	0.00%
Mortgage- and asset-backed securities | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	3.00%	0.00%
Percentage of Total Unrealized Losses	0.00%	0.00%
Public utilities | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	12.00%	16.00%
Percentage of Total Unrealized Losses	6.00%	16.00%
Sovereign and supranational | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	2.00%	3.00%
Percentage of Total Unrealized Losses	1.00%	1.00%
Banks/financial institutions | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	11.00%	12.00%
Percentage of Total Unrealized Losses	12.00%	9.00%
Other corporate | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of Total Investments in an Unrealized Loss Position	59.00%	66.00%
Percentage of Total Unrealized Losses	63.00%	69.00%
Investment Grade | Perpetual securities
Investments, Unrealized Loss Position [Line Items]
Percentage of unrealized losses attributable to securities that were investment grade	100.00%	100.00%
Investment Grade | Japan government and agencies | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of unrealized losses attributable to securities that were investment grade	100.00%	0.00%
Investment Grade | Municipalities | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of unrealized losses attributable to securities that were investment grade	100.00%	0.00%
Investment Grade | Mortgage- and asset-backed securities | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of unrealized losses attributable to securities that were investment grade	100.00%	0.00%
Investment Grade | Public utilities | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of unrealized losses attributable to securities that were investment grade	88.00%	93.00%
Investment Grade | Sovereign and supranational | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of unrealized losses attributable to securities that were investment grade	100.00%	100.00%
Investment Grade | Banks/financial institutions | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of unrealized losses attributable to securities that were investment grade	38.00%	59.00%
Investment Grade | Other corporate | Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Percentage of unrealized losses attributable to securities that were investment grade	47.00%	86.00%